Conventional data communications cables typically comprise multiple pairs of twisted conductors enclosed within a protective outer jacket. These cables often include twisted pair separators in order to provide physical distance (i.e., separation) between the pairs within a cable, thereby reducing crosstalk. Conventional separators are typically made of dielectric materials, such as polyolefin and fluoropolymers, which provide adequate electrical insulation.
Standard materials used in the formation of separators, like polyolefins and certain fluoropolymers, are disadvantageous for a number of reasons. In the event a portion of the cable ignites, it is desirable to limit the amount of smoke produced as a result of the melting or burning of the combustible portions (e.g., a separator) of the cable. It is also desirable to prevent or limit the spread of flames along the cable from one portion of the cable to another. The conventional materials used for cable separators have poor smoke and/or flame-retardant properties. Therefore, those materials increase the amount of smoke that is emitted in the event of a fire, as well as the distance that the flame travels along the burning cable. In order to mitigate these drawbacks, some manufacturers add flame retardants and smoke suppressants to the conventional polyolefin and fluoropolymer materials. However, smoke suppressants and flame retardants often increase the dielectric constant and dissipative factors of the separator, thereby adversely affecting the electrical properties of the cable by increasing the signal loss of the twisted pairs within close proximity to the separator. Also, flame retardants and smoke suppressants generally contain halogens, which are undesirable because hazardous acidic gases are released when halogens burn.
Moreover, the addition of the separator also adds weight to the cable. It is desirable to keep the weight of the cable as low as possible, for ease of transporting to the job site and for reducing the requirements on supports within the building, for example. To reduce the impact on electrical performance and also to reduce the weight of the cable, some manufacturers may “foam” the separators in order to reduce the amount of material used. A foamed material is any material that is in a lightweight cellular form resulting from introduction of gas bubbles during the manufacturing process. However, foaming of conventional separator materials only minimally reduces the amount of material used because the amount of foaming is limited by the resulting physical strength of the foam. The separator must have sufficient strength to prevent damage during cable processing or manufacturing. Additionally, crushing or deformation of the foamed separators can occur if the foamed material does not have adequate strength, resulting in compaction and less separation between twisted pairs. As a result, traditional foamed separators often possess undesirable mechanical stability.
Accordingly, in light of those drawbacks associated with conventional separators, there is a need for a cable separator that adequately reduces crosstalk between twisted pairs within the cable, while simultaneously improving the flame spread and smoke emission properties of the cable without the addition of halogens. Cable separators that are structurally sound and as lightweight as possible are also desirable.